Many miles do you have to drive for the obd to reset in a 2006 325ci?

Every time you start up your vehicle the OBD-II system scans for trouble. This happens at the beginning of every drive cycle when your vehicle is restarted.

Mileage won't have a bearing on when (or if) the system clears itself of trouble codes. Only drive cycles of turning on and off will change that.

Also, note that the system won't turn off the malfunction indicator if a problem is still present. Every time it starts up it will check for problems and as long as the problem still shows up it will continue reading the code and signaling the malfunction indicator (check engine light).

You can try clearing the codes with a scan tool. Even auto parts stores can usually quickly do this for you at no charge. They simply connect their reader to a plug (usually located under the dash on the driver side and easy to access) and have the system cleared of codes.

If the code returns at next start up you know you really have a problem and not just a false problem reading.

In any event, if your OBD system is detecting a problem you should have it scanned for codes to diagnose and repair the problem. Once the problem is solved the codes can be cleared with a scan tool or a few drive cycles will usually clear them on it's own.

Reply to Matt Kesler's Post: Matt - thanks for the reply. I had my codes cleared and the check engine light no longer displays any issues, however, I am trying to get my car through an emissions test and it continues to fail due to "obd readiness". I had a mechanic state that I should drive it a certain amount (100 miles is what they stated) in order to "reset" the computer. Are you stating that the obd resets everytime I turn on the car? If so, should the computer display a ready state?

You can follow a pretty basic readiness process to help with this problem. It likely means the repair was too recent and the vehicle has yet to complete a full cold-to-hot drive cycle.

Here's a generic drive cycle to follow:

* Start the engine. Idle the engine in drive for two or three minutes with the A/C and rear defroster on.
* Turn the A/C and rear defrost off, and accelerate to 55 mph at half throttle.
* Hold at a steady speed of 55 mph for three minutes.
* Decelerate (coast down) to 20 mph without braking or depressing the clutch.
* Accelerate back to 55 to 60 mph at ¾ throttle.
* Hold at a steady speed of 55 to 60 mph for five minutes.
* Decelerate (coast down) to a stop without braking.

Roughly follow this and it should serve to get your OBD to ready. You don't need to be exact or in that order but roughly try to follow that plan.

The computer monitors the system following certain criteria and it may take several drive cycles to reset...here is a site that helps describe the process..pages 5-8 explains in better detail. This may help reset for emissions test. This site is for older BMW's but the parameters are fairly the same. If you have a professional scan tool you can check readiness before going to emissions station CLICK HERE

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